The underhood temperature of a motor vehicle can reach 200.degree. F. during operation, and even 230.degree. F. in extremely hot environmental conditions. Subjecting storage batteries to such excessive temperatures accelerates corrosion of the battery grids, which is a major factor in shortening of battery life. Consequently, the automotive industry has long recognized the need to protect the batteries in motor vehicles from the hot temperatures present in the engine compartment during operation.
Vehicle batteries are conventionally protected from underhood heating by the placement of an insulting shell or shield over the battery. Generally, the shield acts as an insulator. For example, U.S. Pat. No. 5,278,002 to Hiers discloses a box-like battery shield with attachable envelopes of plastic material containing insulation. The heat shield is coupled to the battery by a friction fit along the top and sides of the battery. U.S. Patent to Longardner et al. discloses the encapsulation of a battery with a phase change material. Alternately, the shield may be designed to provide an air gap between the sidewalls of the battery and the shield through which cooler outside air is circulated either by fan or as the result of vehicle motion.
Some insulating shells are designed to be mounted on the battery after it has been installed in the vehicle. For example, U.S. Pat. No. 5,086,860 to Francis et al. discloses a tray upon which the battery is disposed and over which a box placed. The box is secured to the tray by an L-shaped bracket, which extends over the top and one side of the box.
Other heat shields are designed to be assembled onto the battery prior to vehicle installation. It is generally recognized in the automotive industry that creating such a subassembly prior to the final assembly line can reduce overall costs.
For example, U.S. Pat. No. 5,212,025 to Osamu Shibata et al. discloses a storage battery for automobiles which includes a heat shield that is designed to be a part of the battery assembly, making it easier to mount the battery in an automobile. The heat shield is a box-like structure having a closed bottom and which is open at the top to permit the battery to be positioned within the heat shield. The arrangement requires a non-standard cover for the battery to define the air gap and a non-standard container to provide the latching recesses in its for securing the heat shield to the battery. Further, because the heat shield has a closed bottom, the battery must be lifted in order to position it within the heat shield. In addition, this arrangement requires modification of the battery hold down tray and hold down hardware.
U.S. Pat. No. 5,543,248 to Dougherty et al. discloses a clam shell type designs wherein front and rear section halves are coupled to a base by living hinges, or coupled to each other by living hinges. U.S. Pat. No. 5,536,595 to Inkmann et al. and U.S. Pat. No. 4,054,730 to Crifasi disclose a similar two part heat shields which slide onto the battery along its opposite sides to surround the four sides of the battery, the top and bottom being open. The halves are secured together by latches along opposite sides.
While such clam shell shields may be injection molded on a production scale, a number of disadvantages are associated with such clam shell designs. The battery must be assembled into the clamshell prior to assembly into the vehicle. Clamshell side latches are typically not robust enough to assure that shield will remain locked to the battery during installation into the vehicle. Additionally, it is difficult for one person to remove a clam shell heat shield. One person must hold the clamshell open while another removes the battery from the open shield. Further, clamshell designs do not generally lend themselves to easy manual or automated assembly. This results in excessive cost and/or effort to implement on a production basis. Also, clamshells do not typically cover the top of the battery. Covering the top of a battery, however, is critical in extreme operating conditions.